Circuit interrupter



April 15, 1947. y M, CUMMINGI 2,419,123

CIRCUIT INTERRUPTER Filed May 25, 1945 2 Sheets-Sheet l I I 1 I 373931 6145 50 5] 29 WITNESSES: 2. INVENTOR ZZM, 1/4/7765 /W. Caz/772772779.

I Y BY W/QM April 15, 1947. J, M cU 2,419,123

CIRCUIT INTERRUPTER Filed May 25, 1943 2 Sheets-Sheet 2 15 42 fi s? 7 74 76 vhp.z=zsszs; 5 INVENTOR James Cam/7227;.

25 BY I 2? 4w a/W ATTORNEY Patented Apr. 15, 1947 CIRCUIT INTERRUPTER James M. Cumming, Turtle Creek, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa-., a corporation of Pennsylvania Appiication May 25, 1943, Serial No. 488,357

17 Claims.

This invention relates to circuit interrupters in general and, more particularly, to circuit interrupters of the type which utilize the pressure created adjacent one are to force fluid against another serially related arc to effect the latters extinction.

An object of my invention is to provide an improved circuit interrupter in which an improved contact operating mechanism is provided to establish one or more serially related arcs very rapidly. It is desirable in the circuit breaker art to have very high speed operation, such as an interval of three cycles from the tripping of the breaker mechanism to the extinction of the are formed, and to aid in this I provide contact operating means of very high speed.

Another object is to provide an improved contact operating means which will insure that the arcs are not only formed very rapidly, but also are formed in the desired sequence not only during the opening operation but also during the closing operation.

Another object is to provide an improved contact operating means having biasing means which not only biases the contact means toward the open circuit position, but also provides the desired contact pressure between the several contacts.

cuit interrupter in which at least one pressure generating arc and two interrupting arcs are established, and to dispose the arcs in the most effective position to effect their rapid extinction.

Another object is to provide an improved arc extinguishing unit in which the pressure generating arc is established at one end of the unit, a first interrupting arc is established intermediate the ends of the unit and a second interrupting arc is established at the other end of the unit. Preferably the second interrupting are also provides a disconnect break when the second interrupting arc is extinguished.

Another object is to provide an improved contact operating means in which a contact arm is pivotally mounted at one end and to provide contact support means pivoted to an intermediate point of the contact arm.

Another object is to provide a pivoted contact arm with contact support means pivoted to an intermediate point of the contact arm, and to provide stop means carried by the contact support means. The arrangement operates during the circuit opening movement to first rotate the contact arm until the contact arm strikes the stop means, at which time both the contact arm Another object is to provide an improved cirand the contact support means rotate together as a unit. Preferably disconnect means serially connected in the circuit mechanically operate the contact support means to effect the opening and closing of the interrupter.

Another object is to provide rotatable means for establishing a pressure generating arc and also rotatable means for establishing an interrupting arc, and to utilize the pressure created at the pressure generating arc to force fluid under pressure toward the interrupting arc to effect the latters extinction.

Another object is to provide a rotatable means for establishing an are which cooperates with a'second rotatable means which establishes a serially related arc, and also to provide linearly movable means for operating both the aforesaid means. Preferably the linearly movable means constitutes disconnect means in the open circuit position of the interrupter.

Further objects and advantages will readily become apparent upon a reading of the following specification taken in conjunction with the drawings in which:

Figure 1 isan elevational view, partly in section, of a circuit interrupter embodying my invention and shown in the closed circuit position;

Fig. 2 is an enlarged vertical sectional view of one of the improved arc extinguishing units taken on the line IIII of Fig. 6, the parts being shown in the closed circuit position;

Fig. 3 is a view similar to Fig. 2, but showing the disposition of the several parts during the initial portion of the opening operation after the pressure generating arc has been established;

Fig. 4 is a view similar to Fig. 2, but showing the disposition of the parts at a subsequent time during the opening operation when a pressure generating arc and two interrupting arcs have been established;

Fig. 5 is a view in section taken on the line VV of Fig. 4;

Fig. 6 is a view in section taken on the line VIVI of Fig. 4; and

Fig. 7 is a plan view in section taken on the line VII-VII of Fig. 4.

Referring to the drawings and, more particularly, to Fig. 1, the reference numeral I designates a tank filled to the level 2 with a suitable arc extinguishing fluid 3, in this instance oil. Depending from the cover 4 of the tank I are insulating bushings 5, 6 which enclose terminal conductor studs 1, 8. Secured to the lower ends of the conductor studs I, 8 are two identical arc extinguishing units generally designated by the reference numeral 9.

An insulating operating rod it arranged for vertical reciprocating motion by suitable operating means, not shown, serves to move a conducting bridging member ii. The fu ly open circuit position of the conducting bridging member I l is shown by the dotted lines in Fig. l. Briefly, the circuit through the interrupter shown in Fig, 1 comprises the conductor stud l, left-hand are extinguishin unit conducting bridging member ll, right-hand arc extinguishing unit 9 to terminal conductor stud 8. v

Referring more particularly to Fig. 2, it will be observed that a clamp i3 is threadedly secured to the lower end of the conductor stud 'l and clamped thereto by the nut Preferably integrally formed with the clamp i3 is a top metallic plate member l5, in which is threadedly secured a stationary pressure generating contact l8. Disposed intermediate the ends of the arc extinguishunit 9 is a metallic contact plate ll. Interposed between the top metallic plate member l5 and the contact plate ll is an insulating cylinder l8 which holds in position insulating rings i9, 25, the first of which have a larger inside diameter than the latter. The insulating rings i9, 25 form a, substantially enclosed pressure generating chamber or a confined "egion generally designated by the reference numeral 2 l, and having a corrugated inner surface a formed by the rings I9, 26. An over-pressure relief valve 22 may be utilized to prevent excessive pressures being formed in the pressure generating chamber H which otherwise might possibly cause an explosio n.

A plurality of, in this instance six, insulating tie rods 23 hold the several insulating plates in position comprising the unit 5. The tie rods 23 have enlarged head portions 2 3, The upper and lower tie rods 23, as shown in Fig. 5, have their lower ends threadedly secured to the metallic contact plate ll, whereas the other four insulating tie rods 25 extend through the entire unit 9 and have nuts 25 threadedly secured to their lower ends.

A contact arm 2'. is pivotally mounted by means of the pivot pin 25 to the contact plate ll. The contact plate llhas a bifurcated portion 29 (see Fig. 6) which accommodates the pivot pin 28. The contact arm 21 has a laminated resilient conducting portion 55 more clearly shown in Fig. 2. The laminated portion 35 preferably comprises a plurality of resilient metallic blades. Secured, as by soldering, to the lefthand end of the laminated conducting portion 30, as viewed in Fig. 2, is a movable pressure generating contact 3 l, which cooperates with the stationary pressure generating contact I5 to draw a pressure generating are 32 as shown more clearly in Figs. 3 and 4.

A flexible conductor 33 has itsleit-hand end secured, as by spot welding,- to the contact arm 27, and has its right-hand end, as viewed in Fig, 3, secured by the bolts 3-5 to the contact plate ll. A stationary interrupting contact 36 is rigidly secured, as by welding, to the contact plate ii, and cooperates with a first movable interrupting contact 3'! to draw a first interrupting are 38 more clearly shown in Fig. 4. The first movable interrupting contact 3i is disposed at one end of a conducting member 39, the other end of which constitutes a second movable interrupting contact 20, The second movable interrupting contact 4D cooperates with a third movable interill rupting contact 41 to draw a second interrupting are 42 more clearly shown in Fig. 4.

The conducting member 39 is secured, as by the rivets 44, to two insulating plates 45 having a configuration more clearly shown in Figs. 2 and 6. The two insulating plates 45 the conducting member 33 are rigidly secured together by the rivets 44 and move together as a unit. The two insulating plates 3 are pivot-ally mounted inter mediate the ends of the Contact arm 2'! by means of the pivot pin A spring guide rod 41 is also pivotally mounted on the pivot pin 46 and has a washer 45 slidable thereon. A compression spring 5% is disposed between the washer 48 and a second washer 43 disposed at the lower end of the spring guide rod 4'1, a nut 49 being threaded to the lower end of the sprin guide rod 41 to obtain the desired tension in the compression spring 55.

The upper end or" the sprin guide rod 41 is bifurcated to form two legs 5i, more clearly shown in Fig. 6. The legs 51 are disposed between the contact arm 27 and the two insulating plates 45 as more clearly shown in Fig. 6. An insulating stop pin 52 passes through the two insulating plates the purpose for which will appear more clearly hereinafter. Disposed between the contact plate H and the bottom insulating plate 55 of the arc extinguishing unit 9 is a first interrupting arc chamber or first vented region, generally designated by the reference numeral 56, and a second interruptin arc chamber or second vented region, generally designated by the reference numeral 51,

The first interrupting arc chamber 56 comprises a plurality of suitably shaped insulating plates held in position by the insulating tie rods 23. The insulating plates are, in this instance, of two kinds. The first kind is designated by the reference numeral 58 and has an elongated slot 59 formed therein as more clearly shown in Fig. 6. The other kind of insulating plate is designated by the reference numeral 50 and i herein called a vent plate. The vent plate 6% has a vent slot 61 formed therein which in this instance has the same width as the slot 58 formed in the insulating plate 58. However, the vent slot Bl formed in the insulating vent plate has a vent opening 62 more clearly shown in Fig. 6. Consequently, the first interrupting arc chamber 56 is vented to the region exterior of the arc extinguishing unit 9 by the vent openings 52.

Separating the first interrupting arc chamber 58 from the second interrupting arc chamber 51 is an insulating plate 65 having an opening 66 formed therein to accommodate the motion of the spring guide rod 47, and a passage 61 formed therein which serves to provide a fluid conducting passage between the first interrupting arc chamber 55 and the second interrupting arc chamber 51. The insulating plate 65 has a stop portion 58 which serves to limit the downward movement of the conducting member 39. An insulating tube 59 is positioned between the insulating plate 65 and the lowermost insulating plat 55. The tube s' rves as a guide for the compression spring 50.

It will be observed that the washer 48 prevents fluid within the first interrupting arc chamber 55 passing through the opening 55, through the tube 69 and through the vent 15 provided in the bottom insulating plate 55. Consequently, no fiuid passes through the opening 66, all of the flow from the first interrupting arc chamber 55 to the second interrupting arc chamber 51 taking place through the passage El. The bottom insulating plate 55 has an opening H, to accommodate the vertical reciprocating movement of the third movable interrupting contact 4|.

The second interrupting arc chamber 51 comprises, in this instance, three kinds of insulating plates held in position by th insulating tie rods 23. The first kind is herein termed an insulating vent plate 14 and has a configuration more clearly shown in Fig. 7. The insulating vent plate 14 has a vent slot 15 formed therein which terminates into a vent opening 16 as more clearly shown in Fig. 7. The vent plate 14 has an aperture ll formedtherein to accommodate the insulating tube 69.

The second kind of insulating plate constituting the second interrupting arc chamber 51 is herein called an insulating splitter plate 18. It has a splitter portion 79 as a result of having a relatively short elongated slot 8! formed therein. The third kind of insulating plate has a slightly longer elongated slot 8| than the insulating splitter plate It. The slots in the second interrupting chamber are of less width than in the first interrupting chamber to more effectively interrupt low current arcs.

The operation of the interrupter will now be explained. In the closed circuit position of the interrupter, as shown by the full lines in Fig. 1 and by Fig. 2, the electrical circuit passing through the interrupter comprises the terminal conductor 1, the clamp I3, top metallic plate member I5, stationary pressure generating contact I6, movable pressure generating contact 3!, laminated portion 33, contact arm portion 2'5, flexible conductor 33, contact plate ll, stationary interrupting contact 36, first movable interrupting contact 3?, conducting member 3a, second movable interrupting contact 40, third movable interrupting contact 4|, conducting bridging member H from whence the electrical circuit passes through the right-hand arc extinguishing unit 9 in a similar manner toward terminal conductor stud 8. When it is desired to break the electrical circuit passing through the interrupter, or in response to overload conditions in the circuit controlled by the interrupter, suitable operating mechanism, not shown, operates to move the insulating operating rod |i| downwardly. This downward movement of the insulating operating rod it) also moves downwardly the third movable interrupting contact 4|.

The downward movement of the third movable interrupting contact 4| causes the contact arm 21 to rotate in a counterclockwise direction about the pivot pin 28, and causes the insulating plates 45 and the conducting member 39 to rotate in a clockwise direction about the stationary interrupting contact 36 as a fulcrum.

This initial portion of the opening movement serves to draw the pressure generating are 32 as shown more clearly in Fig. 3. The drawing of the pressure generating are 32 within the pressure generating chamber 2| causes pressure to be formed therein. This pressure is vented through the first interrupting arc chamber 55 and through the vent openings 62, and also through the passage 61 and through the vent openings 76 provided in the second interrupting arc chamber The above described opening motion continues until the laminated portion 30 strikes the stop pin 52 as shown in Fig. 3. When this occurs, the contact arm 27, the two insulating plates 45 and the conducting member 39 rotate together as a unit in a counterclockwise direction about the pivot pin 28. This motion, however, serves to draw the first interrupting are 38. The second interrupting are 42 is not drawn at this time since the third movable interrupting contact 4| remains in engagement with the second movable interrupting contact 40.

When the first interrupting are 38 is draw (see Fig. i) there is the first opportunity for interruption of the electrical circuit through the interrupter, for the first interrupting are 38 is subjected to a transverse cross-blast of iluid, in this instance oil, which is caused as a result of the pressure within the pressure generating chamber 25. Consequently, the pressure generating are 32 forces oil against the first interrupting are 35 and may cause the latters extinction even before the second interrupting are 42 is drawn. If such is the case, the electrical circuit through the interrupter will be interrupted, and the separation between the contacts 40, 4| will merely serve to provide the desired disconnest gap. i

However, if the first interrupting are 38 is not extinguished by the pressure generating arc 32 by the time that the conducting member 39 strikes the stop portion 83 of insulating plate 65, then the third movable interrupting contact 4| will separate from the second movable interrupting contact to draw the second interrupting ar =13 clearly shown in Fig. 4. Thus the pressure generating are 32 serves to force oil not only against the first interrupting are 38 but also through the passage 57 in the insulating plate and across the second interrupting are 42 and out through the vent openings 18 provided for the second interrupting arc chamber 5'1. The second interrupting are 42 is forced by the oil flow through the passage 67 to the left, as viewed a, and against the splitter portions 19 of the insulating splitter plates 18. This greatly elongates the second interrupting are 42 and facilitates its extinction. Also the lateral movement of the second interupting are 52 toward the left, as viewed in Fig. 4, brings it into contact with fresh oil of high dielectric strength disposed within the second interrupting arc chamber 51 and also disposed between the splitter portions in of the insulating splitter plates 18.

By a suitable restriction of the Vent openings 62 in the first interrupting arc chamber 56, or even by the elimination of one of the vent openings 62 in the first interrupting arc chamber 56, the first interrupting arc chamber '56 may be somewhat enclosed to assist the pressure generating chamber 2| in forcing oil through the passage 51 and against the second interrupting are 42 in the second interrupting arc chamber 51. In other words, if the first interrupting arc chamber '55 is partly enclosed it will act somewhat as a pressure generating chamber itself to cooperate with the pressure generating are 32 in the pressure generatin chamber 2| to facilitate the extinction of the second interrupting are 42. In the arrangement shown in the drawings, however, the vent openings 62 are sufficiently large so that the pressure generating are 32 forces oil transversely of the first interrupting are 38 and out through the vent openings 62.

The vent openings 16 disposed in the second interrupting arc chamber 51 may be limited so that the second interrupting arc chamber 51 may act somewhat as an explosion pot. Also if the second interrupting are 42 has not been extinguished by the time that the third movable contact 4| has reached the opening 1| in the l bottom insulating plate 55, the second interrupting are 42 will be subjected to a blast of oil as the second interrupting are 42 is drawn through the opening H out of the unit 9. When one of the several arcs is extinguished, this will break the electric circuit through the interrupter and the third movable interrupting contact 41 and the conducting bridging member II will move downwardly to a position shown by the dotted lines in Fig. 1. This provides the desired disconnect gaps in clean oil to prevent reignition of the arcs as a result of voltage surges on the line.

The closing operation of the interrupter will now be explained. During the closing operation the third movable inte *rupting contact 4! moves upwardly to strike the second movable interrupting contact ill. Because of the stop pin 52 the conducting member 32, the two insulating plates 45 and the contact arm 2'! will rotate together as a unit in a clockwise direction about the pivot pin 28 against the biasing action exerted by the compression'spring 50. It will be observed that during this initial closing motion the compression spring 50 produces the desired contact pressure between the second and third movable interrupting contacts 43, M. This motion continues until the first movable interrupting contact 3? strikes the stationary interrupting contact 36, at which time the conducting member 39 and the two insulating plates 45 rotate in a counterclockwise direction about the stationary interrupting contact 35 as a fulcrum, whereas the contact arm 21 rotates in a clockwise direction about the pivot pin 23 until the movable pressure generating contact 3| strikes the stationary pressure generating contact (8. This closes the electrical circuit through the interrupter.

It will be observed that after the first movable interrupting contact 3; has struck the stationary interrupting contact 35 that thereafter the clockwise rotative movement or" the contact arm 21 is exceedingly rapid. Consequently, there is ver little time {or the are which will form between the contacts it, it during the closing operation to generate any gas and contaminate the oil within the pressure generating chamber 2| Also it will be noticed that during the initial portion of the opening operation, whi'e the contacts 36, are in engagement, that the elongation of the pressure gen rating 32 is exceedingly rapid and causes a great anount of pressure to be suddenly formed in the pressure generating chamber 22 because is considerable speed of lengthen of i It will be ap between the c 4- is, lESlllErlLy or the need hy the ortion 33 of contact arin 2?. It will a p arent that the compression sp ng 58 not only biases the entire contact rnech t: 7 the oien circuit position but also produces the desired contact pressure act only between the contacts 45, ii but also be the contacts 3?. This results because of its! W ng plates n '1 I the cor act a rotation wise directic It is appa 3n a counterclo as a fulcrum. the contact arm 2! rotates direction while the insulatstir in 3:? thus permittin the contac arm 2i and the plates to rotate toation. Consequently, although the contact speed is greatly increased by the rotative movement of the parts, nevertheless, the desired sequence of arc dr wing during opening and closing is always maintained.

Although I have shown and described a specific structure, it is to be clearly understood that the same was merely for the purpose of illustration and that changes and modifications may readily be by those skilled in the art without departing from the spirit and scope of the appended claims.

I claim as my invention:

1. In a circuit interrupter, an arc extinguishing unit, a confined region within the unit, means for establishing a pressure generating are within the confined region at one end of the unit, a first vented region, means for establishing a first interrupting a 'c intermediate the ends of the unit in the first vented region, a second vented region, means for establishing a second interrupting are within the second vented region at the other end of the unit, and means utilizing the pressure created within the confined region at the pressure generating arc to force fluid under pressure into the first and second vented regions toward the two interrupting arcs to effect their extinction.

* a circ it in or, an arc extin vithin the unit, a first essure generating are one end of the st interr l l g a c within the first v ed region intermedia'e the ends of the unit, a second vented region, a rd means for establi hing a second interrupt are within the second vented region at the other end or the unit, a portion or" the third means also serving as disconnect means in the open circuit position of the interrupter by being withdrawable from the unit, and means utilizing the pressure created at the pressure generating are within the confined region to force fiuid under pressure into the first and secon vented regions toward the two interrupting arcs to effect their extinction.

3. In a circuit interrupter, an arc extinguishunit, a confined region within the unit, means for establishing a pressure generating are within the confined reg -n at one end of the unit, a first vented region, m ans for establishing a first interrupting are within the first vented region intermediate the ends of the unit after the establishment of the pressure generating are, a second vented region, r 'ei is for establishing a second interrupting arc wi n the second vented region at the other id of he unit after the establishment of the interrupting arc, and means utilising the pressure created within the confined region at the pressure generating arc to force under pressure into the first and second vented regions toward the two interrupting arcs to effect their extinction.

a. In a circuit interrupter, an arc extinguishing unit, a confined region within the unit, a first means for establishing a pressure generating are within the confined region at one end of the unit, a first vented region, a second means to establish a first interrupting are within the first vented region intermediate the "ids of the unit after the establishment of the pressure generatinarc, a second vented region, a third means for estab- 1ishing a second interrupting arc within the sec ond vented region at the other end of the unit after the establishment of the first interrupting are, a portion of the third means also servin 9 as disconnect means in the open circuit position of the interrupter, by being withdrawable from the unit, and means utilizing the pressure created within the confined region at the pressure gencrating arc to force fluid under pressure into the first and second vented regions toward the two interrupting arcs to effect their extinction.

5. In a circuit interrupter, a first relatively stationary contact, a contact arm pivoted at one end and having a first movable contact supported thereon adjacent its other end, the first movable contact being cooperable with the first stationary contact to establish a first arc, a second relatively stationary contact, a second movable contact pivoted on and movable about an intermediate point of the contact arm, the second movable contact being cooperable with the second stationary contact to establish a second arc serially related with respect to the first arc.

6. In a circuit interrupter, a contact arm pivotally mounted on a stationary pivot, contact support means pivoted to an intermediate point of the contact arm, stop means carried by the contact support means, and means operating during the circuit opening operation to first rotate the contact arm until the contact arm strikes the stop means, and to thereafter rotate the contact arm and the contact support means together as a unit.

7. In a circuit interrupter, a substantially en closed chamber, a vented chamber, a first contact means to establish a pressure generating are within the enclosed chamber, the first contact means comprising a contact arm pivotally mounted on a stationary pivot, a second contact 1 means to establish an interrupting are within the vented chamber, the second contact means comprising a contact support member pivoted to an intermediate point of the contact arm, and means operating to first rotate the contact arm to establish the pressure generating arc and subsequently to rotate the contact arm and the contact support member together as a unit to subsequently establish the interrupting are,

8. In a circuit interrupter, a first relatively stationary con act, a contact arm pivotally mounted on a stationary pivot and having a first movable contact adjacent its free end, the first movable contact being cooperable with the first stationary contact to establish an arc, a second relatively stationary contact serially related with respect to the first relatively stationary contact, contact support means pivoted to an intermediate point of the contact arm and carrying a sec. ond movable contact, the second movable contact being cooperable with the second stationary contact to establish an arc, stop means carried by the contact support means, and means for rotating the contact arm until the contact arm strikes the stop means to then permit the contact support means and the contact arm to rotate together a unit.

9. In a circuit interrupter, a substantially enclosed chamber, a vented chamber, passage means extending between the chambers, a first relatively stationary contact, a contact arm pivoted at one end having a first movable contact adjacent its free end, the first movable contact being cooperable with the first stationary contact to establish a pressure generating are within the enclosed chamber, a second relatively stationary contact serially related with respect to the first relatively stationary contact, contact support means pivoted to an intermediate point of the contact arm and carrying a second movcontact support means pivoted to an intermediate point of the contact arm, stop means carried by the contact support means, and serially related disconnect means operating during the circuit opening operation to first rotate the contact arm until the contact arm strikes the stop means, at which time both the contact arm and the contact support means rotate together as unit.

11. In a circuit interrupter, a first elongated rotatable means pivotally mounted at one end for establishing an arc, a second rotatable means for establishing an arc pivotally mounted intermediate the ends of the first elongated rotatable means, and means for connecting the two arcs in series relation.

12. In a circuit interrupter, a first elongated r0- tatable means pivotally mounted at one end for establishing a first arc, a second means pivotally mounted intermedtaie the ends of the first elongated means for establishing a second arc, the two arcs being serially related, stop means carried by the second means, and means operating during the opening operation so that the first and second means initially rotate in opposite di- Iections until the first means strikes the stop means at which time both the first and second means rotate in the same direction.

13. In a circuit interrupter, a first elongated rotatable means pivotally mounted at one end for establishing a first arc, a second means pivotally mounted intermediate the ends of the first elongated means for establishing a second arc, stop means carried by the second means,. and serially related disconnect means including a linearly movable contact striking the second means in abutting engagement operatin during the opening operation so that the first and second means initially rotate in opposite directions until the first means strikes the stop means at which time both the first and second means rotate in the same direction, and the disconnect means being operable to draw a third are between the linearly movable contact and the second means.

14:. In a circuit interrupter, an arc extinguishing unit, a first pair of separable contacts one of which is pivotally mounted at one end within the unit, a second pair of separable contacts one of which is pivotally mounted intermediate the ends or" one of the first pair of contacts, disconnect means for the unit comprising a third pair of separable contacts, means connecting the three pairs of contacts electrically in series, actuating means for the contacts operable to move one of the third pair of contacts, and the actuating means being operable to sequentially cause the separation of the three pairs of separable contacts.

15. In a circuit interrupter, an arc extinguishing unit, a confined region within the unit adjacent one end thereof, a first rotatable means for establishing a pressure-generating are within said confined region, a first vented region intermediate the ends of the unit, a second rotatable mean for establishing a first interrupting arc in the first vented region, a second vented region at the other end of the unit, means for establishing a second interrupting are within the second vented region, and means utilizing the pressure created within said confined region at the pressure generating arc to force fiuid under pressure into the first and second vented regions toward the two interrupting arc to effect their extinction.

16. In a circuit interrupter, an arc extinguishing unit, a confined region within the unit adjacent one end thereof, a first rotatable means for establishing a pressure-generating arc within said confined region, a first vented region intermediate the ends of the unit, a second rotatable means for establishing a first interrupting arc in the first vented region, a second vented region at the other end of the unit, linearly movable means for operating both the first and second rotatable means and for establishing a second interrupting are within the second vented region, and means utilizing the pressure created within the confined region at the pressure generating are to force fiuid under pressure into the first and second vented regions toward the two interrupting arcs to effect their extinction.

17. In a circuit interrupter, an arc extinguishing unit, a confined region within the unit adjacent one end thereof, a first rotatable means for establishing a pressure-generating are within said confined region, a first vented region intermediate the ends of the unit, a second rotatable means for establishing a first interrupting arc in the first vented region, a second vented region at the other end of the unit, linearly movable means for operating both the first and second rotatable means and for establishing a second interrupting are within the second vented region. means utilizing the pressure created within the confined region at the pressure generating arc to force fiuid under pressure into the first and second vented regions toward the two interrupting arcs to effect their extinction, and the linearly movable means being withdrawn from the unit to insert an isolating gap in the circuit in the fully open circuit position of the interrupter.

JAMES M. CUMMING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,151,551 Ishiwata Mar. 21, 1939 1,956,049 Schweitzer Apr. 24, 1934 1,299,457 Gray Apr. 8, 1919 2,098,801 Erben Nov. 9, 1937 2,292,547 Sadler Aug. 11, 1942 891,722 OBrien June 23, 1908 1,473,838 Driessen Nov. 13, 1923 1,792,496 Hinshaw Feb. 17, 1931 2,282,687 Vigren et al May 12, 1942 1,949,258 Paul Feb. 27, 1934 

